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NAME

       ssh_sftp - SFTP client.

DESCRIPTION

       This module implements an SSH FTP (SFTP) client. SFTP is a secure, encrypted file transfer
       service available for SSH.

DATA TYPES

       sftp_option() =
           {timeout, timeout()} |
           {sftp_vsn, integer() >= 1} |
           {window_size, integer() >= 1} |
           {packet_size, integer() >= 1}

   Error cause
       reason() = atom() | string() | tuple()

              A description of the reason why an operation failed.

              The atom() value is  formed  from  the  sftp  error  codes  in  the  protocol-level
              responses  as  defined  in  draft-ietf-secsh-filexfer-13 section 9.1. The codes are
              named as SSH_FX_* which are transformed into lowercase of the star-part.  E.g.  the
              error code SSH_FX_NO_SUCH_FILE will cause the reason() to be no_such_file.

              The  string()  reason  is the error information from the server in case of an exit-
              signal. If that information is empty, the reason is the exit signal name.

              The tuple() reason are other errors like for example {exit_status,1}.

   Crypto operations for open_tar
       tar_crypto_spec() = encrypt_spec() | decrypt_spec()

       encrypt_spec() = {init_fun(), crypto_fun(), final_fun()}

       decrypt_spec() = {init_fun(), crypto_fun()}

              Specifies the encryption or decryption applied to tar files when  using  open_tar/3
              or open_tar/4.

              The  encryption  or decryption is applied to the generated stream of bytes prior to
              sending the resulting stream to the SFTP server.

              For code examples see Section Example with encryption in the ssh Users Guide.

       init_fun() =
           fun(() -> {ok, crypto_state()}) |
           fun(() -> {ok, crypto_state(), chunk_size()})

       chunk_size() = undefined | integer() >= 1

       crypto_state() = any()

              The init_fun() in the tar_crypto_spec is applied once prior  to  any  other  crypto
              operation.  The  intention  is  that  this  function  initiates  the  encryption or
              decryption  for  example  by   calling   crypto:crypto_init/4   or   similar.   The
              crypto_state() is the state such a function may return.

              If  the  selected  cipher  needs  to have the input data partioned into blocks of a
              certain size, the init_fun() should return the second form of return value with the
              chunk_size()  set  to the block size. If the chunk_size() is undefined, the size of
              the PlainBins varies, because this is intended for stream crypto, whereas  a  fixed
              chunk_size()  is  intended  for  block crypto. A chunk_size() can be changed in the
              return from the crypto_fun(). The value can be changed  between  pos_integer()  and
              undefined.

       crypto_fun() =
           fun((TextIn :: binary(), crypto_state()) -> crypto_result())

       crypto_result() =
           {ok, TextOut :: binary(), crypto_state()} |
           {ok, TextOut :: binary(), crypto_state(), chunk_size()}

              The  initial  crypto_state()  returned  from the init_fun() is folded into repeated
              applications of the crypto_fun() in the tar_crypto_spec. The binary  returned  from
              that  fun  is  sent to the remote SFTP server and the new crypto_state() is used in
              the next call of the crypto_fun().

              If the crypto_fun() reurns a chunk_size(), that value is as block size for  further
              blocks in calls to crypto_fun().

       final_fun() =
           fun((FinalTextIn :: binary(), crypto_state()) ->
                   {ok, FinalTextOut :: binary()})

              If  doing encryption, the final_fun() in the tar_crypto_spec is applied to the last
              piece of  data.  The  final_fun()  is  responsible  for  padding  (if  needed)  and
              encryption of that last piece.

EXPORTS

       apread(ChannelPid, Handle, Position, Len) -> {async, N} | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Position = Len = integer()
                 Error = {error, reason()}
                 N = term()

              The apread/4 function reads from a specified position, combining the position/3 and
              aread/3 functions.

       apwrite(ChannelPid, Handle, Position, Data) -> {async, N} | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Position = integer()
                 Data = binary()
                 Error = {error, reason()}
                 N = term()

              The apwrite/4 function writes to a specified position, combining the position/3 and
              awrite/3 functions.

       aread(ChannelPid, Handle, Len) -> {async, N} | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Len = integer()
                 Error = {error, reason()}
                 N = term()

              Reads  from  an  open file, without waiting for the result. If the handle is valid,
              the function returns {async, N}, where N is a term guaranteed to be unique  between
              calls  of  aread. The actual data is sent as a message to the calling process. This
              message has the form {async_reply, N, Result}, where Result is the result from  the
              read, either {ok, Data}, eof, or {error, reason()}.

       awrite(ChannelPid, Handle, Data) -> {async, N} | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Data = binary()
                 Error = {error, reason()}
                 N = term()

              Writes to an open file, without waiting for the result. If the handle is valid, the
              function returns {async, N}, where N is a term  guaranteed  to  be  unique  between
              calls  of  awrite.  The  result  of the write operation is sent as a message to the
              calling process. This message has the form {async_reply, N, Result},  where  Result
              is the result from the write, either ok, or {error, reason()}.

       close(ChannelPid, Handle) -> ok | Error

       close(ChannelPid, Handle, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Timeout = timeout()
                 Error = {error, reason()}

              Closes a handle to an open file or directory on the server.

       delete(ChannelPid, Name) -> ok | Error

       delete(ChannelPid, Name, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Deletes the file specified by Name.

       del_dir(ChannelPid, Name) -> ok | Error

       del_dir(ChannelPid, Name, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Deletes a directory specified by Name. The directory must be empty before it can be
              successfully deleted.

       list_dir(ChannelPid, Path) -> {ok, FileNames} | Error

       list_dir(ChannelPid, Path, Timeout) -> {ok, FileNames} | Error

              Types:

                 ChannelPid = pid()
                 Path = string()
                 Timeout = timeout()
                 FileNames = [FileName]
                 FileName = string()
                 Error = {error, reason()}

              Lists the given directory on the server, returning  the  filenames  as  a  list  of
              strings.

       make_dir(ChannelPid, Name) -> ok | Error

       make_dir(ChannelPid, Name, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Creates a directory specified by Name. Name must be a full path to a new directory.
              The directory can only be created in an existing directory.

       make_symlink(ChannelPid, Name, Target) -> ok | Error

       make_symlink(ChannelPid, Name, Target, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Name = Target = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Creates a symbolic link pointing to Target with the name Name.

       open(ChannelPid, Name, Mode) -> {ok, Handle} | Error

       open(ChannelPid, Name, Mode, Timeout) -> {ok, Handle} | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 Mode = [read | write | append | binary | raw]
                 Timeout = timeout()
                 Handle = term()
                 Error = {error, reason()}

              Opens a file on the server and returns a handle, which can be used for  reading  or
              writing.

       opendir(ChannelPid, Path) -> {ok, Handle} | Error

       opendir(ChannelPid, Path, Timeout) -> {ok, Handle} | Error

              Types:

                 ChannelPid = pid()
                 Path = string()
                 Timeout = timeout()
                 Handle = term()
                 Error = {error, reason()}

              Opens  a  handle  to  a directory on the server. The handle can be used for reading
              directory contents.

       open_tar(ChannelPid, Path, Mode) -> {ok, Handle} | Error

       open_tar(ChannelPid, Path, Mode, Timeout) -> {ok, Handle} | Error

              Types:

                 ChannelPid = pid()
                 Path = string()
                 Mode = [read | write | {crypto, tar_crypto_spec()}]
                 Timeout = timeout()
                 Handle = term()
                 Error = {error, reason()}

              Opens a handle to a tar file on the server, associated with ChannelPid. The  handle
              can  be used for remote tar creation and extraction. The actual writing and reading
              is  performed  by  calls  to  erl_tar:add/3,4  and  erl_tar:extract/2.  Note:   The
              erl_tar:init/3  function  should not be called, that one is called by this open_tar
              function.

              For code examples see Section SFTP Client with TAR Compression  in  the  ssh  Users
              Guide.

              The  crypto  mode  option  is explained in the data types section above, see Crypto
              operations for open_tar. Encryption is assumed if  the  Mode  contains  write,  and
              decryption if the Mode contains read.

       position(ChannelPid, Handle, Location) ->
                   {ok, NewPosition} | Error

       position(ChannelPid, Handle, Location, Timeout) ->
                   {ok, NewPosition} | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Location =
                     Offset |
                     {bof, Offset} |
                     {cur, Offset} |
                     {eof, Offset} |
                     bof | cur | eof
                 Timeout = timeout()
                 Offset = NewPosition = integer()
                 Error = {error, reason()}

              Sets  the file position of the file referenced by Handle. Returns {ok, NewPosition}
              (as an absolute offset) if successful, otherwise {error, reason()}. Location is one
              of the following:

                Offset:
                  The same as {bof, Offset}.

                {bof, Offset}:
                  Absolute offset.

                {cur, Offset}:
                  Offset from the current position.

                {eof, Offset}:
                  Offset from the end of file.

                bof | cur | eof:
                  The same as eariler with Offset 0, that is, {bof, 0} | {cur, 0} | {eof, 0}.

       pread(ChannelPid, Handle, Position, Len) ->
                {ok, Data} | eof | Error

       pread(ChannelPid, Handle, Position, Len, Timeout) ->
                {ok, Data} | eof | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Position = Len = integer()
                 Timeout = timeout()
                 Data = string() | binary()
                 Error = {error, reason()}

              The  pread/3,4  function  reads from a specified position, combining the position/3
              and read/3,4 functions.

       pwrite(ChannelPid, Handle, Position, Data) -> ok | Error

       pwrite(ChannelPid, Handle, Position, Data, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Position = integer()
                 Data = iolist()
                 Timeout = timeout()
                 Error = {error, reason()}

              The pwrite/3,4 function writes to a specified position,  combining  the  position/3
              and write/3,4 functions.

       read(ChannelPid, Handle, Len) -> {ok, Data} | eof | Error

       read(ChannelPid, Handle, Len, Timeout) -> {ok, Data} | eof | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Len = integer()
                 Timeout = timeout()
                 Data = string() | binary()
                 Error = {error, reason()}

              Reads  Len  bytes  from  the file referenced by Handle. Returns {ok, Data}, eof, or
              {error, reason()}. If the file is opened with binary, Data is a  binary,  otherwise
              it is a string.

              If the file is read past eof, only the remaining bytes are read and returned. If no
              bytes are read, eof is returned.

       read_file(ChannelPid, File) -> {ok, Data} | Error

       read_file(ChannelPid, File, Timeout) -> {ok, Data} | Error

              Types:

                 ChannelPid = pid()
                 File = string()
                 Data = binary()
                 Timeout = timeout()
                 Error = {error, reason()}

              Reads a file from the server, and returns the data in a binary.

       read_file_info(ChannelPid, Name) -> {ok, FileInfo} | Error

       read_file_info(ChannelPid, Name, Timeout) ->
                         {ok, FileInfo} | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 Timeout = timeout()
                 FileInfo = file:file_info()
                 Error = {error, reason()}

              Returns a file_info record from the file system object specified by Name or Handle.
              See file:read_file_info/2 for information about the record.

              Depending  on  the  underlying  OS:es links might be followed and info on the final
              file, directory etc is returned. See read_link_info/2 on how to get information  on
              links instead.

       read_link(ChannelPid, Name) -> {ok, Target} | Error

       read_link(ChannelPid, Name, Timeout) -> {ok, Target} | Error

              Types:

                 ChannelPid = pid()
                 Name = Target = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Reads the link target from the symbolic link specified by name.

       read_link_info(ChannelPid, Name) -> {ok, FileInfo} | Error

       read_link_info(ChannelPid, Name, Timeout) ->
                         {ok, FileInfo} | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 FileInfo = file:file_info()
                 Timeout = timeout()
                 Error = {error, reason()}

              Returns  a file_info record from the symbolic link specified by Name or Handle. See
              file:read_link_info/2 for information about the record.

       rename(ChannelPid, OldName, NewName) -> ok | Error

       rename(ChannelPid, OldName, NewName, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 OldName = NewName = string()
                 Timeout = timeout()
                 Error = {error, reason()}

              Renames a file named OldName and gives it the name NewName.

       start_channel(ConnectionRef) ->
       start_channel(ConnectionRef, SftpOptions) -> {ok, ChannelPid} | Error
       start_channel(Host) ->
       start_channel(Host, Options) ->
       start_channel(Host, Port, Options) ->
       start_channel(TcpSocket) ->
       start_channel(TcpSocket, Options) -> {ok, ChannelPid, ConnectionRef} | Error

              Types:

                 Host = ssh:host()
                 Port = inet:port_number()
                 TcpSocket = ssh:open_socket()
                 Options = [ sftp_option() | ssh:client_option() ]
                 SftpOptions = [ sftp_option() ]
                 ChannelPid = pid()
                 ConnectionRef = ssh:connection_ref()
                 Error = {error, reason()}

              If no connection reference is provided,  a  connection  is  set  up,  and  the  new
              connection   is  returned.  An  SSH  channel  process  is  started  to  handle  the
              communication with the SFTP server. The returned pid for this process is to be used
              as input to all other API functions in this module.

              Options:

                {timeout, timeout()}:
                  There are two ways to set a timeout for the underlying ssh connection:

                  * If  the  connection timeout option connect_timeout is set, that value is used
                    also for the negotiation timeout and this option (timeout) is ignored.

                  * Otherwise, this option (timeout) is used as the negotiation timeout only  and
                    there is no connection timeout set

                  The value defaults to infinity.

                {sftp_vsn, integer()}:
                  Desired SFTP protocol version. The actual version is the minimum of the desired
                  version and the maximum supported versions by the SFTP server.

              All other options are directly passed to ssh:connect/3 or ignored if  a  connection
              is already provided.

       stop_channel(ChannelPid) -> ok

              Types:

                 ChannelPid = pid()

              Stops  an SFTP channel. Does not close the SSH connection. Use ssh:close/1 to close
              it.

       write(ChannelPid, Handle, Data) -> ok | Error

       write(ChannelPid, Handle, Data, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Handle = term()
                 Data = iodata()
                 Timeout = timeout()
                 Error = {error, reason()}

              Writes data to the file referenced by Handle. The file is to be opened  with  write
              or append flag. Returns ok if successful or {error, reason()} otherwise.

       write_file(ChannelPid, File, Data) -> ok | Error

       write_file(ChannelPid, File, Data, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 File = string()
                 Data = iodata()
                 Timeout = timeout()
                 Error = {error, reason()}

              Writes  a  file  to  the  server.  The  file  is  created  if it does not exist but
              overwritten if it exists.

       write_file_info(ChannelPid, Name, FileInfo) -> ok | Error

       write_file_info(ChannelPid, Name, FileInfo, Timeout) -> ok | Error

              Types:

                 ChannelPid = pid()
                 Name = string()
                 FileInfo = file:file_info()
                 Timeout = timeout()
                 Error = {error, reason()}

              Writes file information from a file_info record to the file specified by Name.  See
              file:write_file_info/[2,3] for information about the record.